Just wanted to add my 2 cents - since this poppes up every now & then...
You should go for 2 networks, this simplifies everything. But please remember (and this goes for all, see example like this thread http://forum.linuxmce.org/index.php/topic,13316.0.html
2 networks can easily and happily work on 1 physical network, and 1 network card can just as easily have 2 IP addresses! So in this concrete example:
Set the IP of the router to 10.0.0.1 (netmask 255.255.255.0) - disable DCHP
Set external ip on your core to 10.0.0.2 (on card eth0), gateway 10.0.0.1
Set internal ip on core to 192.168.0.1 on card eth0, which is referred to as eth0.0...
From a logical point of view you have 2 networks, and every issue with regards to the internal workings of LMCE is unaffected. Any machine in your network will never become aware of the fact that you are running 2 logical networks in the same physical wires.. It is completely transparent, except for instances that relies on broadcasts - but just concern yourself with letting that run in the 192.168 network - and it will if you just let DHCP run from the core, and nowhere else..
So even if you mixed up netmask with logical network topology, your idea works - and the only real drawback in your suggestion is the overhead that comes from enlarging the subnet.. So stick with class C subnets (255.255.255.0). Your LMCE DHCP server will route the traffic anyway..
ok, this question is moot for me now, I need a new wifi-ap anyway, and then I'll just go for the recommended setup.
Thanks for the input anyway.